In order for an automotive lighting assembly to be mounted in an automobile, the lighting assembly must fit within a small defined space that is specifically designed for that automobile's automotive lighting assembly. Consequently, the automotive lighting assembly must be as compact as possible. Automotive lamp housings typically have several studs attached to their exterior or interior for use in mounting the lamp housing on an automobile. Sometimes the studs are threaded to allow fine adjustment or positioning of the lamp housing to control the direction of the light beam, while other studs may be relatively smooth to fit into a corresponding slot for alignment. Regardless of the nature or use of the stud, the stud must be attached to the lamp housing with sufficient strength in order to allow the lamp housing to attach to a corresponding anchor on an automobile.
One common method and assembly for connecting a stud to a lamp assembly is shown in FIG. 1. As shown in FIG. 1, a double-sided stud 30 with two threaded portions 16 is mated with an integrally molded plastic mounting boss 28 of a lamp housing 20 by inserting one of the threaded portions 16 into the mounting boss. Lamp housing 20 is molded with bosses 28 by means known to those skilled in the art. After stud 30 is inserted into boss 28 and prior to mounting the lamp housing to a mounting panel 18, a plate 29 is attached to stud 30 by means well known in the art. A foam gasket 33 is then attached to stud 30 so that it sits adjacent to the backside of plate 29. The lamp housing 20 is then attached to the mounting panel 18 of an automobile by inserting the threaded portion 16 opposite the lamp housing through an opening 17 that passes through the mounting panel. Once inserted, foam gasket 33 is pinched between plate 29 and mounting panel 18 in order to seal opening 17 and a nut 19 is tightened on the stud to attach the lamp housing to the mounting panel. Boss 28 of lamp housing 20 will sit against the plate 29 once the lamp housing 20 is connected to the mounting panel. Unfortunately, a double-sided stud mated with an integrally molded boss limits the design flexibility of a manufacturer and prevents a manufacturer from being able to further reduce the size of the total lamp assembly, because the boss needs to be of sufficient size to allow the stud to mate with the lamp housing without effecting the internal workings of the lighting assembly.
Aside from limiting design options, the double-sided stud and integral molded mounting boss assembly leads to other problems. For example, manufacturing lamp housings to include integrally molded bosses complicate the designs of molds and the molding process. Complicated molds not only increase costs, but also increase the possibility of mold failure during the manufacturing process.
Further, referring to FIG. 1, the plate 29 leads to a lot of variation between the connections of the lamp housing designed for a particular line of automobiles. On the manufacturing line, each automobile design has a plurality of lamp assemblies specifically designed to fit into lighting compartments on the automobile. Thus, lighting manufacturers design and make several of the same lamp assembly for each of these compartments in order to allow the manufacturing of a particular line of automobiles. Unfortunately, even though the automobiles are made the same and the lamp assemblies are made the same, there are sources of variations that cause each of a particular lamp assembly to fit differently in each of the particular compartments of a line of automobiles. Such variations lead to gaps in between the automobile's lighting compartment and the lighting assembly. Manufacturers spend a lot of time, energy and cost eliminating these gaps by placing seals around the lighting assemblies in order to, have an aesthetically pleasing automobile.
Referring back to FIG. 1, the plate 29 causes variation in the lamp assembly connection between the automobile and lamp assembly, because the plate will not be of the same size or of the same depth, even though the plates are made from the same process. Thus, each lamp assembly will be sitting on plates 29 that vary in depth and size. It is accepted and general manufacturing error that leads to this variation and leads to gaps between the lamp housing and automobile. However, it is desired to eliminate or at least decrease the variation from automobile to automobile in order to save money and time during manufacturing of the automobile.
To get around some of the problems associated with the two-sided stud and integrally molded boss connection, designers have searched for alternate ways to mount the stud to the lamp housing. One such method involves spin welding a single-sided stud to the lamp housing. FIG. 2a shows a perspective view of one known embodiment of a stud 10 that can be spin welded to a lamp housing (shown in FIGS. 3a and 3b). As shown in FIG. 2a, stud 10 is a molded plastic stud that has a cap 12 and a post 14. Cap 12 has a relatively flat surface with spiral ridges 15 and has ears 13 positioned thereon. In operation, a pneumatic tool (not pictured) fits onto the ears 13. Cap 12 is placed on the surface it is to be welded too, such as lamp housing 20, and then spun by the tool. As stud 10 spins the spiral ridges 15 create friction and heat between plastic cap 12 and a corresponding plastic lamp housing 20 until the cap and lamp housing are melted and ultimately welded together. Ears 13 will break away when the ideal melt point is reached and will prevent any further rotation of stud 10 by the tool. Stud 10 is then held against lamp housing 20 until the weld sets. Unfortunately, such an embodiment does not allow for a metal stud to be attached to a lamp housing, which ultimately leads to a weaker connection between the lamp housing and automobile.
To overcome this disadvantage, a stud assembly was created that joined a single-sided, metal stud with a plastic collar that cold be spin welded to a lamp housing. FIG. 2b shows a cross section view of a stud assembly 21 that comprises a metal stud 22 with a cap 23 and a post 32 with a threaded portion 16. As shown in FIG. 2b, stud assembly 21 further comprises a collar 24 that is molded over stud 22 so that cap 23 sits in a recess 25. Collar 24 has a face 26 and ears 13. Just as with stud 10, a pneumatic tool can be used to spin weld stud assembly 21 to a lamp housing 20 (shown in FIGS. 3a and 3b). The tool can connect to the ears 13 and spin face 26 against the lamp housing 20 until the lamp housing and stud assembly are welded together. Ears 13 will break away when the ideal melt point is reached, which will prevent any further rotation of stud assembly 21 by the tool. Stud assembly 21 is held against lamp housing 20 until the weld sets. FIG. 3a shows stud assembly 21 spin welded to a thin lamp housing 20 and mounted to mounting panel 18. As shown in FIG. 3a, face 26 is welded together with a section of lamp housing 20 at a weld interface section 27. Stud assembly's 21 threaded portion 16 is inserted through opening 17 on mounting panel 18 on the automobile and fastened to the panel by a nut 19.
The problem that plagues spin welded studs and/or stud assemblies is that during the welding process the cap and/or collar are usually driven into lamp housing to some degree. As the heat increase and pressure increases, the lamp housing melts which causes the stud and/or stud assembly to drive into the lamp housing. This causes variation in the amount of space that is in between the lamp housing and mounting panel (i.e. the depth of the collar that separates the lamp housing and panel varies depending on how far the collar is driven into the lamp housing). As discussed above, such variations cause gaps between the automobile and lamp assembly which must be plugged up for, among other reasons, aesthetic reasons. Such a process adds time and expense to the automotive assembly process.
A further draw back with spin welded stud assemblies is they can only easily and inexpensively be used with thin lamp assemblies that have a housing that will ultimately be in close proximity with the mounting panel (as shown in FIG. 3a). If used in normal lamp assemblies, the lamp assemblies would have to be molded with raised surfaces on the back of the lamp housing so that the stud would be able to be in close proximity and attached to the mounting panel. FIG. 3b shows stud assembly 21 welded to a normal lamp housing 20. As shown in FIG. 3b, lamp housing 20 has a raised area 34 that allows assembly 21 to be welded to the lamp housing and mounted to mounting panel 18. Like the double-sided stud and integrally molded boss connection, such raised surfaces lead to complicated mold designs and mold failure, which increases the cost of manufacturing lamp assemblies. Moreover, after installing lamp assemblies with spin welded studs and/or stud assemblies, it has been determined that the weld is inconsistent and ultimately, subject to failure.
Accordingly, what is needed is a method and assembly that increases design flexibility and allows a manufacturer to further decrease the size of the lamp assembly. Further, what is needed is a method and assembly for allowing a stud to be added to an automotive lamp housing that reduces the manufacturing costs and possibility of mold failures. More particularly, what is needed is a method and assembly that allows a stud assembly to be attached to any lamp assembly with a stronger, more consistent weld joint and a method and assembly that reduces variation and promotes a more accurate fit between the lamp housing and automobile. These and other advantages of the subject invention will be understood from the below description.